Known dry transformers are used, for example, in electrical power distribution systems or in local power systems, such as, in marine applications. Dry power transformers can be available within voltage levels, for example, between 1 kV and 60 kV with a rated power in-between 100 kVA and several MVA. Dry transformers can reduce the use of oil as an insulation and cooling medium, can have reduced maintenance, lessen the fire load, and can provide for higher environmental friendliness. However, where no liquid cooling medium is used to circulate around the transformer coils, cooling can be needed. Due to electrical losses during operation of a transformer, for example, the transformer coils can be a heat source for heat energy.
The insulation material of a transformer coil can be characterized by a rated temperature, for example, 150° C. If this temperature is exceeded, a loss of the insulation ability might be the consequence. Also the electric conductor of the transformer coil, which is made, for example, out of copper or aluminium, should not exceed a certain limit. The electric resistance of the conductor can rise with increasing temperature and the electrical losses therewith. Therefore, a temperature distribution within the transformer coil, which can be homogenous and avoid punctual stress, can be desirable.